The present invention relates to a control system for a web material cutting line, and more particularly to a control system for controlling the cutting of web material of indeterminate length into sheets of predetermined length.
In continuous web material cutting lines having a so-called payoff or supply reel for supplying elongated narrow web material, and a web shearing or cutting device located near the forward or downstream end of the cutting line for cutting of the web material to sheets of predetermined length, there are provided, between the supply reel and the web cutting device, various devices and instruments, such as a side trimmer for trimming the sides of the web material, a leveler for holding the traveling web material flat, a thickness meter, a pin-hole detector and other inspection devices. Such a web cutting line needs a substantial distance between the supply reel and the web cutting device. When stopping the cutting of the web with a great part of the web material remaining on the supply reel, it is quite hard to rewind the web material in the cutting line on the supply reel.
Some of such web material cutting lines are provided with shearing or cutting devices for cutting off that part of the web material remaining along the cutting line after stoppage. Such a cutting device (which is hereinafter referred to as an end cutting shear) is located near the entrance of the cutting line through which the web material is introduced to the cutting line. The desired number of standard sheets obtainable from that part of the web which is disposed along the cutting line is estimated, based on an effective or acceptable rate. When the sum of the estimated number of possible acceptable sheets and the number of cut off sheets reaches a predetermined total or desired number of sheets, the end cutting shear is actuated to cut off that part of the web that is still disposed along the cutting line. Such a control system has been disclosed in Japanese Unexam. Patent Publ. No. 60-135,111.
If an accurate number of acceptable or standard sheets is to be obtained, a highly reliable effective acceptable rate must be used. To provide a reliable rate, it is necessary to run the web cutting line for quite a long period of time. Therefore, it is hard to obtain a reliable rate when cutting only a small number of sheets.